The Sherline won't do threads unless something has changed (haven't been to
their site for a while) so that lathe is out. I'd go with something larger
anyway as you will always like the additional cap. of a larger lathe. A 10"
or 12" Craftsman or Atlas lathe is usually a good lathe to have and are
often available for fairly cheap.
I might also note that I'm not a fan of the multimachines as they tend not
to do any particular chore very well.

--
Bob May
Losing weight is easy! If you ever want to lose weight, eat and drink less.
Works evevery time it is tried!